Maximally insulin-stimulated glucose uptake in skeletal muscle, ie, insulin responsiveness, is reduced in fed animals as compared with fasted animals; but acute prior endurance exercise improves insulin responsiveness in the muscles of fed rats. The effect of acute prior sprint interval exercise on insulin responsiveness in the muscles of fed animals has not been clarified, and we therefore compared the effect of short high-intensity swimming as a model of sprint interval exercise on insulin responsiveness in the muscles of fed rats with the effect of prolonged low-intensity swimming as a model of endurance exercise. The fed rats were subjected to an acute bout of high-intensity intermittent swimming (HIS) or low-intensity continuous swimming (LIS). The HIS rats swam for eight 20-second periods with a weight equal to 18% of their body weight. The LIS rats swam with no load for 3 hours. HIS increased (P < .05) the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) Thr(172) and that of its downstream target acetyl-CoA carboxylase (ACC) Ser(79) 12.6- and 3.1-fold, respectively, whereas LIS increased them 3.8- and 1.9-fold, respectively, immediately after exercise compared with rested muscle. HIS and LIS increased the insulin responsiveness of 2-deoxyglucose uptake measured 4 hours after exercise by 39% and 41%, respectively, compared with rested muscles. These results show that very short (160 seconds) HIS exercise with greater AMPK activation increases the responsiveness of glucose uptake to insulin in the muscles of fed rats to a similar level observed after prolonged (3 hours) LIS exercise with lower AMPK activation. Therefore, it is suggested that an acute bout of sprint interval exercise that activates AMPK to a sufficiently high level can increase post-exercise insulin responsiveness on muscle glucose uptake irrespective of very short exercise duration.